Psycho's "shower scene" begins as a
baptism scene. Marion has just decided to escape her self-imposed
trap by returning the money, and is taking a cleansing shower...
(DVD ch 10)

Despair

Norman: We're all in our private traps - clamped in
them. And none of us can ever get out. We scratch and we claw, but
only at the air, only at each other, and for all of it we never
budge an inch.
Marion: Sometimes we deliberately step into those traps.
Norman: I was born in mine. I don't mind it anymore.
Marion: Oh, but you should. You should mind it!
Norman: Oh, I do. But I say I don't. (DVD ch 8)

Hiding Sin/Evil

Norman Bates watches the car with Marion's body in
it, sink into the water, and become enveloped by the lake. (DVD ch
12) At the end of the movie, the car is brought back up from the
lake, as the truth is discovered.